Analysis Of Outage Performance In The Stratosphere Collaborative Communication System With Df

Stratospheric communication is a key node to integrated space-air-land communications network in the future, it has unique advantages compared with the ground communication and setellite communication, gradually become a hot topic in the recent years. However, in the communication process of stratospheric platform and ground users, especially when the user is in low elevation coverage area of the stratospheric platform and mountain or woodland environment, due to the impact of large-scale fading will cause deterioration in its communication performance, even communication outage. To solve this problem, this paper introduces cooperative relay technology to enhance the performance of stratospheric communication systems.In this paper, using the outage performance of bidirectional links of the stratospheric cooperative communication system as research content, including the following aspects:First, the transmission characteristics of the stratospheric platform communication system channels are analyzed, learn the channel characteristics of stratospheric platform communication from previous research results, establish a heterogeneousa channel model conforms to the stratosphere communication features, in which describe the channel between ground nodes by Nakagami-m distribution, describe the channel between ground node and stratospheric platforms by Lognormal distribution. On the other hand, consider the base station using the decode and forward(DF) way, the channels from the stratospheric platform to different ground nodes may suffer the same obstruction, therefore, this paper proposes to use shadow related Lognormal statistical channel model to describe the distribution of stratospheric platform to statistical channel between ground nodes.Secondly, the outage performance of a single base station cooperative stratospheric communication systems are analyzed. According to the relevant principles of information theory, deduce the outage probability expressions of the DF synergistic system. For the uplink, use the moment generating function(MGF) matching method to approximate two Lognormal random variables as a new Lognormal random variable. For downlink, through the analysis find that sum of a Lognormal random variable with a Nakagami-m random variables can be approximated as a new Lognormal random variable, also use MGF matching method to get the new parameter Lognormal random variable. On this basis, the outage probability of the system can be cacluated. Simulation results show that: i) Direct channel under poor transmission quality, the collaboration can significantly improve the outage performance of the system; ii) Lognormal parameters(?,?) and Nakagami-m parameter m, have a significant impact on the outage probability of the cooperative system; iii) In the uplink, the correlation between the Lognormal channels also affect the outage probability of the system, the larger the correlation, the greater the outage probability.Finally, further analysis the outage performance of the stratospheric communication system using multiple base stations with DF protocol. For the uplink, promote MGF matching method to handle the distribution of sum of multiple Lognormal random variables. For the downlink, may prove the sum of independent and identically distributed Nakagmi-m random variables remains a Nakagami-m random variables. On this basis, further calculates the outage probability. Simulation results show that: i) Direct communication channel quality is poor, multiple base stations cooperation can more significantly improve the performance of the communication; ii) In the multiple base station cooperative system, the influence of channel fading parameters on the system outage probability is relatively small, it shows from the side multisite collaborative system interrupts the performance of obvious advantages; iii) The number of ralays is not negligible impact, the number N is large, the outage probability is small.